The screwed joint is the most commonly used connection in mechanical engineering. Such joining elements can be effective only by use of appropriate installation tools. Torque tools as mentioned above, belong to the suitable installation tools for this purpose. Torque tools are required to exert a certain torque on a workpiece. Known torque tools are, for example, torque wrenches or torque screwdrivers.
The torque transferred when using hand-held tools is dependent both on the physical condition of the user as well as his subjective feeling of power. Torque tools are used to load a high prestressing force to a screw which is within the elastic range of the screw, or to load the screw with only small preload forces. The use of new construction materials such as magnesium, aluminum or plastic, especially for lightweight construction in the automotive or aerospace industry, increases both the need and the requirements for torque tools. By the use of these new materials, the number of sensitive screw connections is increasing. The lower tensile strength of lightweight materials compared to steel materials would lead to damage of the thread if overstressing the screwed connection, which would make these expensive components unusable.
Torque wrenches with a digital torque display are disclosed by prior art DE 20 2008 005 705 U1. DE 20 2007 018 043 U1 describes a torque wrench in which the displayed digits are highlighted by an illuminated display. In doing so, a certain torque range is signalized to the user by the color. Especially when working in places with obstructed view readability is difficult.
The utility model DE 20 2009 002 124 U1 discloses a torque wrench with a display unit which is arranged on the tool shaft of the torque wrench. On the display unit at least two different optical signals can be displayed. The display unit annularly surrounds the tool shaft. As a result, an optical signal for recognizing the applied torque is emitted in all radial directions of the circumference of the display unit so that a user can recognize without a clear view on the display module, to which torque range a just applied torque belongs. For generating the optical signals at least one light emitter is provided in the display unit, for example in the form of light emitting diodes (LEDs).
As Head-up display a display panel is denoted, in which the head may be left up while reading the display. The display panel is always in sight. A field of view display is a display system in which information for a user, such as pilots, is projected into his field of view. This technique has been known in the aviation technology. More recently, this technique has been also utilized in the automotive industry. The head-up display typically consists of a projector, which generates an image, and a projection area. The projection area is a reflective and translucent glass. A suitable optical arrangement with collimator and diversion directs the image on the projection area. Thus, a user of a head-up display recognizes the reflected information which is generated by the projector, and the real world located behind the projection area at the same time. In aviation special small picture tubes are used to generate the appropriate image. Picture tubes produce very high luminosity, and therefore no additional light source is required. On the other hand, LEDs are also often used as a light source. The brightness of the image is controlled in dependence on the ambient light by a photo sensor. Thus, the image is generated by a high-resolution color TFT display.
German Patent Application DE 10 2012 206 962 A1 provides a head-up display, which generates a virtual image to an observer. The virtual image is displayed on a reflector, which is formed by a windshield or the like. For this purpose light of a head-up unit (projector) is reflected from the projection screen. A head-up unit includes a light source that emits light for displaying a video. Furthermore, the projector includes a minor, which controls the optical path of light, and a concave lens for displaying on the windscreen.
German Patent Application DE 10 2011 001 429 A1 discloses a conventional vehicle head-up display which is also known as HUD device. The HUD device displays a light emitting image on a display and projects the display image onto a projection element, such as a windshield. Accordingly, the HUD device displays a virtual image of vehicle-related information. One kind of such a HUD device provided as a vehicle head-up display is a device which reflects a display image of a display on a reflecting mirror, for example a concave minor, and projects the reflected image to a projection element. This HUD device comprises a display, an optical system, a motor and a reduction gear mechanism. The display is configured to display a light emitting image. The optical system includes a reflection minor, which is arranged rotatable relative to the display to reflect the image displayed by the display. The optical system is configured to project the image reflected at the mirror to a projection element of the vehicle, and thereby displaying a virtual image of vehicle-related information on the projection element. The motor is configured to generate a torque to adjust a rotation angle of the mirror in accordance with an external setting instruction. The virtual image can be displayed in a displayable area of the rotational angle of the mirror.
In view of the above, one of the objects of the invention is to provide a display system for a torque tool which facilitates a weight reduction of the torque tool itself. Another object of the invention is to develop a display system that provides the user with substantial information without distracting the user from main work functions.